Beijing was covered by smog on Friday with the China Environmental Monitoring Center's reading showed the air quality ranging between poor and hazardous in the city, signifying the first air pollution spike of the new year.

Weather forecast authorities in the capital issued a yellow alert at 5 pm on Friday, warning that heavy fog will continue and urging residents with respiratory diseases to stay indoors.

The PM2.5 (particles less than 2.5 microns) data in Beijing hit 240 to 446 on Friday, signifying heavily polluted air.

Air quality ratings for the city have ranged between "very unhealthy" and "hazardous" since Thursday and PM 2.5 reading by press time was 413, according to @BeijingAir, a Twitter account run by the US embassy in Beijing.

Beijing is not alone in suffering heavy air pollution, with fog also hitting many parts of China on Friday.

The National Meteorological Center issued a blue alert for fog early Friday morning for Beijing, Tianjin, and provinces including North China's Hebei, Shanxi and East China's Anhui, Zhejiang and Central China's Henan, Hubei and Southwest China's Sichuan.

The center also forecast that fog will continue on Saturday morning with visibility in areas such as Hebei, Beijing, Tianjin, Henan, Shandong, Jiangsu, Hubei and Sichuan dipping to below 1,000 meters and some regions with visibility dropping below 200 meters.

Demands for better air quality were made on Friday online with more than 7.4 million Web users discussing the bad weather, as smog had already caused dozens of cities and provinces to see heavy pollution.

Experts warned drivers to be more careful about their safety and suggested they take protective measures such as wearing masks if they had to travel.

Global Times - Xinhua